0510800 JOHNSON SPRING, Lower

Recommended Procedure
1. Air in Fuel System ... With air in the fuel system the engine will normally be difficult to start, run rough and release a large amount of white smoke. To remove the air from the fuel system, open the manual bleed valve on the fuel injection pump housing. Operate the priming pump until the flow of fuel from the manual bleed valve is free of air. Close the manual bleed valve and fasten the fuel priming pump. Start the engine. If the engine still does not run smooth or releases a large amount of white smoke, loosen the fuel line nuts one at a time at the cylinder heads, and permit the fuel to come out until it is free of air. Tighten the fuel line nuts. If air is not removed in this way, put 5 psi (35 kPa) of air to the fuel tank.
Do not use more then 8 psi (55 kPa) of air pressure in the fuel tank or damage to the tank may result.
Check for leaks at the connections between the fuel tank and the fuel transfer pump. If leaks are found, tighten the connections or replace the lines. If there are no visual leaks, remove the fuel supply line from the tank and connect it to an outside fuel supply. If this corrects the problem, the suction line (standpipe) inside the fuel tank has a leak.2. Valve Adjustment Not Correct ... Check and make necessary adjustments as per Testing and Adjusting Section of this Service Manual. Intake valve clearance is .015 in. (0.38 mm) and exhaust valve clearance is .025 in. (0.64 mm). Also check for a bent or broken push rod.3. Fuel Injection Timing Not Correct ... Check and make necessary adjustments as per Testing and Adjusting Section of this Service Manual.4. Automatic Timing Advance Does Not Operate Correctly ... Check with engine warm. Use the 8T5300 Timing Indicator Group to check the automatic timing advance unit. Check to see that the advance is smooth and that the amount of advance is correct. See Fuel System of the Testing and Adjusting section of this Service Manual for the subject CHECKING ENGINE TIMING AND AUTOMATIC TIMING ADVANCE UNIT WITH 8T5300 TIMING INDICATOR GROUP. If the timing indicator is not available, make rapid "acceleration" (increase in speed) from low idle to high idle. Engine must have smooth acceleration. A timing advance that does not operate correctly can cause delays of the engine acceleration at some rpm before high idle, or possibly cause the engine to run rough and have exhaust noise (backfire) during acceleration. This condition is difficult to find if engine acceleration is slow or at a constant engine rpm.5. Bad Fuel Nozzle(s) ... Find a bad nozzle by running engine at the rpm where it runs rough. Loosen the fuel line nut at the cylinder head enough to stop fuel supply to that cylinder. Each cylinder must be checked this way. If a cylinder is found where loosening of the nut makes no difference in the rough running, test the nozzle for that cylinder. To test a nozzle, remove the nozzle from the engine and test as per Testing and Adjusting section of this Service Manual.6. Valve Leakage; Wear or Damage to Pistons and/or Piston Rings; Wear or Damage to Cylinder Walls ... The condition of these parts can be checked with a cylinder leakage tester. Special Instruction, Form No. GMG00694, gives the test procedure. The components can be bad if leakage is more than the specifications. If leakage is heard at the inlet manifold, the intake valves leak. If the leakage is heard at the exhaust manifold, the exhaust valves leak. If leakage is heard at the oil filler opening, the piston rings leak.7. Cylinder Head Gasket Leakage ... Check with the cylinder leakage tester. If leakage is higher than specifications, check at the fuel nozzle hole of the next cylinder to see if the leak is between cylinders. Leakage at the gasket of the cylinder head can show as an outside leak or can cause loss of coolant through the radiator overflow.8. Engine Camshaft Timing Not Correct ... Engine camshaft timing can be checked by finding the top center position for number one cylinder as per Testing and Adjusting section of this Service Manual. If timing is not correct remove the front cover and check timing marks. If timing marks are correct check for a broken drive dowel in the camshaft drive gear.9. Fuel Leakage from Fuel Injection Line Nut ... Tighten nut to 30 5 lb.ft. (40 7 N m). Again check for leakage.10. Fuel Has a High "Cloud Point" ... The fuel "cloud point" is the temperature at which wax begins to form in the fuel. If the atmospheric temperature is lower than the "cloud point" of the fuel, wax will form and plug the filter. Change the filter and drain the tank and the complete fuel system. The replacement fuel must be of a better grade with a lower "cloud point".